Device for axially retaining a cylindrical element and more particularly a cable

ABSTRACT

The invention concerns a device for axially retaining a cylindrical element and more particularly a cable ( 1 ) comprising a socket ( 7, 9 ) with an external thread and extended in the axial direction by clamping plates ( 9 ), and an overlapping nut ( 6 ) comprising internally a shrunk pressure surface ( 11 ) designed to act on the ends of the clamping plates ( 9 ) of the socket and radially deform them towards the cylindrical element ( 1 ) previously inserted into said socket after passing through said not ( 6 ). Said device is in particular characterised in that it further comprises a sleeve ( 8, 10 ) likewise provided with clamping plates ( 10 ) and whereof the external diameter is not larger than the internal diameter of the socket wherein said sleeve is designed to be inserted starting with said plates ( 10 ) with which it is provided, said socket being further internally provided with a shrunk pressure surface ( 12 ), designed to act on the sleeve clamping plates ( 10 ). In one embodiment, a packing seal is further provided.

[0001] The present invention relates to a device for axial maintenanceof a cylindrical element and more particularly a cable.

[0002] For fixing a cylindrical element into another element, such asfor example, an electric cable into the coupling bushing of a plug orelectricity socket, or furthermore, for example, into a conduit, a tubeor pipe in an apparatus or accessory, it is known how to use deviceswhich maintain said cylindrical element against traction efforts.

[0003] For this, a device for axial maintenance is known comprising anaxial maintenance device for a cylindrical element and more particularlyfor a cable, comprising a coupling bushing which is threaded externallyand which is prolonged in the axial direction by tightening nut strips,and a covering nut comprising internally a reduced pressure surfaceintended to act on the ends of the nut strips of the coupling bushingand to deform them radially towards the cylindrical element previouslyintroduced into said coupling bushing after crossing said nut.

[0004] This type of device is, for example, described in the Frenchpatent 2358766 or again in the European patent 0381980.

[0005] In the French patent cited above, the device furthermorecomprises a packing seal and thus constitutes both a compression glandor stuffing box.

[0006] In this device known in prior art, the packing deforms into atruncated cone and the adhesion of the cable is active over a limitedlength.

[0007] Furthermore, the deformation of the packing is not well containedinternally and each device can only concern a restricted number ofelements to fix, in a relatively reduced range of diameters.

[0008] Finally, in such a device, there cannot be any strip anchoring inthe element to be held since any traction on the latter tends toseparate said strips.

[0009] Among other things, the invention makes it possible to improvethe traction resistance performances of this type of device, especiallyin order to fulfil the anti-deflagration standards relative to thedomain of electrical apparatuses.

[0010] In order to do this, a device according to the invention of thetype described above is particularly notable in that it furthercomprises a sleeve also provided with nut strips and whose externaldiameter is at most equal to the internal diameter of the couplingbushing in which said sleeve is intended to be introduced beginning bysaid strips with which it is provided, said coupling bushing beingfurther provided internally with a reduced pressure surface, intended toact on the nut strips of the sleeve.

[0011] According to an embodiment, the pressure surface of the couplingbushing and the sleeve are dimensioned so that the strips of said sleeveanchor into the cylindrical element during the tightening of the nut.

[0012] In order to ensure tightness, the invention envisages anembodiment which is provided with a tubular sealing packing intended tobe inserted in final position between the cylindrical element, thesleeve and the coupling bushing strips.

[0013] For example, in this case, the sealing packing is in two parts ofdifferent external diameters, the smallest external diametercorresponding substantially to the internal diameter of the sleeve andthe biggest diameter corresponding substantially to the internaldiameter of the coupling bushing.

[0014] A device according to the invention which remains compact andwhich only requires a single screwing operation also makes it possibleto ensure, with a single device, both the anchoring and the sealing ofvarious cables in a large range of diameters, which simplifies thechoice of the user, limits storage problems and raises manufacturingvolumes, thus reducing production costs.

[0015] The invention will be better understood and other particularitieswill become clear by reading the following description which refers tothe attached drawings in which:

[0016]FIG. 1 is an exploded view of a device according to the invention.

[0017]FIG. 2 is an axial cross-section of the various elements to beassembled.

[0018]FIGS. 3, 4 and 5 are axial cross-sections of the device of FIGS. 1and 2, respectively before screwing the nut, at the beginning ofscrewing and at the end of screwing.

[0019]FIG. 6 is a view corresponding to FIG. 5 according to another veryslightly different embodiment.

[0020] The figures represent a device according to the inventionintended to fix, in the example shown, an electric cable 1 (FIGS. 3 to6) in a bush 2 of an electrical connection means (coupling bushing of aplug or mobile plug or of an extension or connector etc.) The deviceaccording to the invention comprises a coupling bushing 3 integral withthe bush 2, a sleeve 4, a packing seal 5 in rubber and a ring shaped nut6.

[0021] As shown clearly in the diagrams, the coupling bushing 3 and thesleeve 4 are provided with a base 7 and a base 8 respectively, prolongedby strips 9 and 10 respectively which protrude externally in the axialdirection, the strips 10 of the sleeve 4 being positioned for assembly,as explained below, towards the strips 9 of the coupling bushing 3(FIGS. 1 and 2). The base 7 of the coupling bushing 3 is furtherprovided with an external threading as shown in the drawings, intendedto co-operate with the internal threading of the nut 6.

[0022] At the base of its threading the nut 6 has an internal pressuresurface 11 reduced for example in truncated form whose function will beexplained below.

[0023] In the same way, the base of the coupling bushing 3 is, on theopposite side from the strips 9, provided with a reduced internalpressure surface 12.

[0024] As shown clearly in the drawings, the packing 5 has two parts 5 aand 5 b in steps of different external diameters.

[0025] The smallest external diameter (part Sa) of the packing 5corresponds substantially to the internal diameter of the base 8 of thecoupling bushing 3 and the biggest diameter (part 5 b) correspondssubstantially to the internal diameter of the strips 9 of the sleeve 4before deformation, while the external diameter of said sleeve 4 issubstantially equal to the internal diameter of the coupling bushing 3.

[0026] The drawings show clearly the way in which to assemble togetherthe various elements of the device.

[0027] The elements are initially arranged as shown in FIGS. 1 and 2.

[0028] Beginning from this assembly, the sleeve 4 is introduced by itsstrips into the coupling bushing 3, and after or before, the part 5 a isintroduced into the packing 5 in the base 8 of the sleeve 4 and thecovering nut 6 is set in place on the strips 9 of the coupling bushing 3in order to be in the position of FIG. 3.

[0029] Before or after this first assembly, the cable 1 is evidentlyintroduced through all the elements (2, 3, 4, 5 and 6).

[0030] Starting from the position of FIG. 3, the nut 6 is pushed whichitself pushes the packing assembly 5 and sleeve 4 until the strips 10 ofthe sleeve 4 are held radially by the pressure surface 12 of thecoupling bushing 3 to be deformed and to be tightened onto the cable 1as shown in FIG. 4.

[0031] Next the screwing of the nut 6 is carried out which accentuatesthe deformation of the strips 10. By continuing said screwing of the nut6, the strips 9 of the coupling bushing 3 tighten radially on thepacking 5 by deforming under the effect of the pressure surface 11 ofsaid nut 6.

[0032] In the embodiment of FIGS. 1 to 5, the length of the sleeve 4 andthe pressure surface 12 of the coupling bushing 3 are such that thestrips 10 of said sleeve 4 are anchored at the end of screwing in thecable 1 as shown in FIG. 5.

[0033] In the embodiment of FIG. 6, the base 8 of the sleeve 4 is lesslong axially and/or the strips 10 are shorter as well as the pressuresurface 12, in such a way that in this embodiment, said strips 10 do notanchor in the cable 1. Given that the differences of the sleeve and thesurface 12 of the coupling bushing 3 of the device of FIG. 6, relativeto the sleeve 4 and the coupling bushing 3 of FIGS. 1 to 5 areessentially dimensional, the same references have been kept on saidfigures.

[0034] On FIGS. 5 and 6, it can be seen that the packing 5 is perfectlycompressed by the sleeve 4 and the strips 9 of the coupling bushing 3,and furthermore it is perfectly maintained between its two ends by thestrips 9 and 10 of the coupling bushing 3 and the sleeve 4 respectively.

[0035] Compared to prior art, the invention enables a greater length ofcontact between the packing 5 and the cable 1 together with a greatervolume of deformed packing, which increases the reliability of thesealing and retention, thus ensuring a greater reserve of elasticity tocompensate for the relaxation of plastic parts intended to compress thepacking.

[0036] The strips of the coupling bushing 3 act on the packing 5 and thecable 1 in a classic way whereas the strips 9 of the sleeve 4 act in theopposite direction with, further, an anchoring or not, in the cable 1(FIGS. 5 and 6 respectively).

[0037] Furthermore it can be understood that in the embodiment of FIGS.1 to 5, any traction on the cable accentuates the anchoring of thesleeve 4, said anchoring thus being self-blocking.

[0038] If the embodiment relates in particular to an electric cable, itcan evidently concern, as explained above, any cylindrical element.

1. Device for axial maintenance of a cylindrical element and moreparticularly of a cable (1), comprising a coupling bushing (3) which isthreaded externally and which is prolonged in the axial direction bytightening nut strips (9), and a covering nut (6) comprising internallya reduced pressure surface (11) intended to act on the ends of the nutstrips (9) of the coupling bushing (3) and to deform them radiallytowards the cylindrical element (1) previously introduced into saidcoupling bushing (3) after crossing said nut (6), the devicecharacterised in that it further comprises a sleeve (4) also providedwith nut strips (10) and whose external diameter is at most equal to theinternal diameter of the coupling bushing (3) in which said sleeve (4)is intended to be introduced beginning by said strips (10) with which itis provided, said coupling bushing (3) being further provided internallywith a reduced pressure surface (12), intended to act on the nut strips(10) of the sleeve (4).
 2. Device according to claim 1 characterised inthat the pressure surface (12) of the coupling bushing (3) and thesleeve (4) have dimensions such that the strips (10) of said sleeve areanchored in the cylindrical element (1) during the tightening of the nut(6).
 3. Device according to either one or the other of claims 1 and 2characterised in that it is provided with a tubular packing seal (5)intended to be inserted in the final position between the cylindricalelement (1), the sleeve (4) and the strips (9) of the coupling bushing(3).
 4. Device according to claim 3 characterised in that the packingseal (5) is in two parts (5 a, 5 b) with different external diameters,the smallest external diameter corresponding substantially to theinternal diameter of the sleeve (4) and the biggest diametercorresponding substantially to the internal diameter of the couplingbushing (3).